1. Field of the Invention
The present invention pertains to the manufacture of flexible packages, such as plastic bags, and in particular to packages having fastener closures employing sliders.
2. Description of the Related Art
With the recent emphasis in providing consumers with bulk quantities of various commodities, such as food products, reclosable packages have become increasingly popular. One of the most popular means of providing reclosability is to employ zippers of various types, particularly zippers which are compatible with flexible packages of plastic film construction. Manufacturers of food products and other commodities are concerned with filling the contents of a flexible package as quickly and economically as possible. It is important that the opening provided by the fastener be made as large as practically possible. Consumers or other end users also prefer large sized openings for easy extraction of products from the package interior. Even with large openings, however, products within the package may interfere with fastener operation when product poured or otherwise dispensed from the package becomes entrained in the fastener components.
Other improvements to flexible reclosable packages are being sought. For example, when handling products comprised of numerous small pieces, such as shredded cheese or cereal, for example, it is generally desirable to have the package formed into a pouch which is open at one end, or along one side, so as to allow product to be poured or shaken through the reclosable opening. It is desirable that the product be allowed to freely flow past the reclosable opening. Preferably, the path taken by the product within the package should be made as smooth as possible.
Although improvements have been made in the art of plastic welding and joining, manufacturers of consumer products employing high speed production techniques are continually seeking improved package forming methods and equipment.
It is an object of the invention to provide apparatus for manufacturing improved flexible packages.
Another object of the invention is to provide apparatus for making reclosable packages having fastener sliders which are protected as the package contents are poured out or otherwise extracted.
A further object of the invention is to provide apparatus for making a reclosable plastic package having a slider fastener with improved containment of the slider in a manner which also optimizes the size of the bag opening.
A further object of the invention is to provide apparatus for making a plastic bag having a slider fastener with an improved endxe2x80x94xe2x80x9ccrushxe2x80x9d stop of the fastener tracks.
These and other objects of the invention are attained in a vertical form-fill seal machine for the in-line manufacturing of food packages having zipper slider closures. The machine includes a supply of web material extending in a machine direction, including a chain or serial succession of food package portions extending in the machine direction. A supply of fastener track with male and female zipper parts is provided. The collar member receiving web material. The web drive transports web material over collar in the machine direction, folding the web into overlying side-by-side portions, one against the other to form a pair of overlying package walls. The supply of slider members are mateable with the fastener track for movement along the fastener track in opposite directions to open and close the fastener track. The slider installation member engages slider members with the fastener track. A pair of zipper seal bars seals to the package wall a portion of the fastener track extends in the machine direction. A pair of peel seal bars extends in the machine direction for forming a peel seal coupled between the package walls. A pair of spaced-apart side seal bars extends at an angle to set machine direction and seal portions of the package walls together to form respective side seals of the food package. The side seal bars and peel seal bar cooperate with the second seal bar to form a closed package.
It has been found difficult in a practical commercial environment to reliably employ conduction heat sealing techniques to form the slider stop. It is preferred that the stop be formed using ultrasonic sealing techniques, as these afford greater control over dimension and shape. This is important when the frontal surface area of the stop (and optionally, the overall mass) is reduced to the greatest extent possible.